Primarily for general aviation discussion, but other aviation topics are also welcome.
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By PaulB
It’s clear that moving map GPS software has, especially over the last decade or so, changed the way that many of us plan and execute our flights. The software, not only produce plogs without the need for a whizz wheel, but also handle weather, NOTAMs and can als (when configured) handle things such as weight and balance and fuel management.

One area where we seem to be still in the middle of the previous century is take-off and landing performance calculations.

There is guidance on the CAA website about factors for grass etc, but the actual calculation still requires rulers and pencils and graphs from the POH that even for a relatively new aircraft, look like they were created in 1934. Add to that that many are US based so have weights in lbs and distances in feet (whereas we use kg and m) and it seems like a recipe for something that is much harder than it ought to be.

Are there any software packages out there that will do this and if there are, how do you enter the appropriate parameters to “set it up” for your aircraft as the lines on the graphs are not straight.
Dodo liked this
For those of us that mostly fly off grass, it's all spurious accuracy. So many factors in play that can't be measured, i.e. how soft the ground is, how long the grass is, how damp ot is etc
Personally I'd positively discourage a calculation driven approach as it would either have to be ridiculously cautious and hence discredited, or risks giving too much confidence to the calculation.
A fast taxi run is my preference where necessary.
mick w, Miscellaneous, mmcp42 and 9 others liked this
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By PaulB
Those are very valid points. I fly from a very long, very smooth hard runway. When I flew an ageing (both in airframe and engine terms) PA28 I used to mentally note where I rotated each flight. It was remarkably consistent - because I assume the conditions were largely consistent.
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By Dodo
A friend of mine converted the Take off Graph for our group owned PA28-181 to an excel spreadsheet that works out the Take off Run and also the distance required to 50 ft.

I'll make him aware of this thread so that if he wants to share it publicly, he can.
TheFarmer wrote:There are simply too many variables, and too many people who’d take it as gospel and then try and sue someone when their Tomahawk ended up in a hedge.

,,,,,,,,,,,,,,,,,,,or , how can I get my tablet device to spoon-feed me even more than it does already .
Your 'app' won't tell you if your prop. is contaminated with bugs along the leading edge , or if your wheel-spats are already full of grass , or if your engine compressions could do with a bit of a top-end overhaul , or if your air filter element requires a clean out , or if your tyre pressures are a bit low .

Holding any sort of pilot licence requires a basic working knowledge of what makes an aeroplane fly and what doesn't . There are certain parts of that responsibility that cannot be 'teflonned' off onto a piece of software .

As TF says , far too many variables .
Nick, Lockhaven, Shoestring Flyer and 2 others liked this
Somewhat surprised at some of the views so far to be honest. Calculating performance figures for your aircraft is a key licensing skill, and conceptually it gives you an idea of whether your intended runway/loading is suitable for the conditions - additional factors will always make it more conservative on top. If you really intend to operate with stuff like engine deficiencies or an bogged Runway, well then all bets are off whatever. Most of the take off and landing incidents I have seen are because people have operated to / from blatantly unsuitable runways because ‘the know their aircraft best’ and ‘we’ve always landed there ok’
PaulB, Ben K liked this
PaulB wrote:Does Foreflight use the CAA factors?

What are CAA factors?

EDIT: Just researched this, and it seems that yes, Foreflight does indeed use the same factors for calculating performance. The nice thing about it is that it pulls all the required weather, runway and aircraft data automatically. All you have top do is tell it which aircraft and runway you wish to use. Very quick and very accurate.
Last edited by brucehumblehand on Sat Sep 07, 2019 11:01 am, edited 1 time in total.
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By PaulB
brucehumblehand wrote:
PaulB wrote:Does Foreflight use the CAA factors?

What are CAA factors?

(No idea if these are the most up to date ones (which raises more issues if they're not)
Available on iTunes is a free take-off and landing performance calculator for General Aviation pilots I wrote a few years ago for GASCo. Work out the take-off and landing distance required for your aeroplane (airplane). Created using the United Kingdom Civil Aviation Authority Safety Sense Leaflet 7 factors for correction of un-factored take-off and landing distance calculations. Easily work out the effect on take-off and landing performance due to factors such as weight, slope, temperature, and wind.

Great for students pilots, qualified pilots, and flight instructors to quickly see the significant effect which multiple variables have on take-off and landing performance. Whether you're a PPL (Private), CPL (Commercial) or ATPL (ATP), this app will help you to evaluate the effect of a number of runway threats during your pre-flight planning.

Available as GASCo Performance Calculator for your iPad or GASCo Performance mini for your iPhone.

Created for and on behalf of the General Aviation Safety Council based in the United Kingdom. GASCo was founded in 1964 to provide a forum in which all of the General Aviation organisations could meet to share safety information. In addition to the Council Meetings for the member organisations, GASCo has its own magazine GASCo Flight Safety available free on iTunes.

iPad version - GASCo Performance Calculator ... d942306086

iPhone version - GASCo Performance mini ... d943457606

Top tip: if you set the "unfactored TODR / LDR" to 100 in the App, it gives you the difference as a percentage of your original Take-Off Distance Required. i.e. an unfactored distance of 100 which gives a factored distance of 200 would then mean that you need twice the distance in those conditions.

I hope you find it useful!

MichaelP, Flyin'Dutch' liked this
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By MichaelP
Always try to have a go/no go decision point in mind if you are uncertain as to whether your aeroplane will fly.

I have used this successfully many times, but recently, twice I have been caught out when due to someone else doing the takeoff making a fundamental mistake and then giving me control or me having to take control. Now my choice was crash for definite or have faith in my ability to fly off in ground effect.
I chose to fly both times.
The first time I learned about the practical use of ground effect, I love ground effect!
This was applied to the second time.
The first time I ran the calculations the night before, and added the factors involving grass...
The second should have been a lot easier, it was off a hard runway but with a 1.6% upslope.

Takeoff performance charts are for ideal performance both by the pilot and by the aeroplane.
Keep the nosewheel on the ground, or even raise the tail too soon, and the run will be longer.
Raise the nose too high or hold the tailwheel on the ground and the run will be longer.

When a short run is required you need to ignore the published rotate speed in the flight manual in a single engine aeroplane unless it’s a high wing loading jet.
Cessna 150/152/172, PA28’s etc will fly well before their ‘rotate’ speeds are reached, and many such aeroplanes have a similar speed for best angle climb, meaning they’re expected to be airborne at below the ‘rotate’ speed.
Last edited by MichaelP on Sat Sep 07, 2019 12:40 pm, edited 1 time in total.
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By MichaelP
I have had pilots do both a takeoff and a landing calculation for the same runway/strip.

If the sum of takeoff and landing distances is less than the length available you can pick a decision point somewhere in the middle.
If the sum is greater than the length available then you must judge your go/no go decision point accordingly.
Some will say have 75% of your takeoff speed at the halfway point, but you must apply your gut feeling too, based on your knowledge of the aeroplane, estimation of the surface, and sense of the wind, elevation, and temperature.

[ - Takeoff roll - ] + [ - Landing roll - ]

[ - Runway length available - ] less or more than the sum above?